Stent-graft

ABSTRACT

A stent-graft comprises: a graft defining an elongate lumen having a longitudinal axis; an external stent having a plurality of struts and apices between the struts, the apices including proximal apices and distal apices; a set of proximal sutured knots, the proximal sutured knots securing the proximal apices of the stent to the graft; a set of distal sutured knots, the distal sutured knots securing the distal apices of the stent to the graft; and a plurality of intermediate sutured knots, formed along a continuous suture, the continuous suture including a plurality of bridging portions, the bridging portions bridging between neighbouring struts of the stent, the intermediate sutured knots securing struts of the stent to the graft.

RELATED APPLICATIONS

The present application claims the benefit of the filing date under 35U.S.C. § 119(e) of Provisional U.S. Patent Application Ser. No.62/716,444, filed Aug. 9, 2018, and also claims priority to AustralianPatent Application No. 2018214103, filed on Aug. 9, 2018, issued asPatent No. 2018214103 on Jan. 17, 2019, which are hereby incorporated byreference in their entireties.

BACKGROUND 1. Technical Field

The present invention relates generally to the field of medical devices.Particular embodiments are related to medical devices that aredeployable into bodily lumens including vascular systems, and especiallyto stent-grafts and their manufacture.

2. Background

Stents grafts for insertion into a body passageway, such as a vascularpassageway or other body lumen are used in situations where thepassageway or lumen may have a defect, such as a stenosis or ananeurysm. Stents perform functions that make them useful in combinationwith grafts. A stent can resist pressure on a graft, and help to providesupport for a blood vessel. A stent can provide an outward pressure tokeep the graft and hence the lumen open. A stent can also beself-expanding so as to deploy a stent-graft from a compressed andradially compact condition to an expanded deployed condition. A stentmay also be used to anchor the graft in place, where anchors or barbs onthe stent are provided. Such anchors can secure the stent, and hence thegraft, in the desired location within a lumen of a patient.

Typically, stents are attached to grafts using sutures.

A difficulty with known stent-grafts is the complexity and assemblyprocess time required for manufacture. Complexity introduces potentialfor mistakes.

A further issue with some known stent-grafts is bio-burden. That is,some stent-grafts are known to occasionally release suture material intoa patient.

A yet further issue with some known stent-grafts is residual holes leftin the graft after temporary or tacking stitches are removed.

BRIEF SUMMARY

The present invention seeks to provide an improved endoluminalprosthetic device or other medical device, such as a stent graft, and animproved method of forming an endoluminal prosthetic device.

According to an aspect of the invention, there is provided a stent-graftcomprising:

a graft having an elongate lumen and a longitudinal axis;

at least one stent having a plurality of struts and an apex between eachof the plurality struts, the apices including proximal apices and distalapices;

a running suture attaching the stent to the graft, the running suturecomprising:

first and second knots knotted along the length of each of at least somestruts of the plurality of struts at intermediate points spaced from theproximal and distal apices of said at least some struts,

a length of running suture running between the first and second knots,and

a first bridging portion extending between a first knot on a first strutand a first knot on a second strut next adjacent the first strut, and asecond bridging portion extending from a second knot on the second strutto a second knot of a third strut next adjacent the second strut.

Advantageously, the first bridging portion is proximal to the secondbridging portion.

Preferably, the first bridging portion extends between two struts of aproximal apex and the second bridging portion extends between two strutsof a distal apex.

The first bridging portion preferably extends between a first strut of afirst proximal apex and a first strut of a second proximal apex.

A length of the bridging portions may pass in and out of the graftbetween next adjacent struts.

The stent graft may comprise a series of proximal tack knots securingthe one or more of the proximal apices of the stent to the graft; and/ora series of distal tack knots securing one or more of the distal apicesof the stent to the graft.

Preferably, the series of proximal and/or distal tack knots areconfigured such that the stent can slide relative to the graft.

The stent graft may comprise a third knot in the running suture betweeneach of the first and second knots.

In the preferred embodiments, the bridging portions are disposedtransverse to the longitudinal axis of the lumen.

Each strut of the plurality of struts advantageously has a first knotand a second knot and a first bridging portion extending from the firstknot and a second bridging portion extending from the second knot.

It is preferred that the running suture is a single continuous length ofsuture.

According to another aspect of the present invention, there is provideda stent-graft comprising:

a graft having an elongate lumen and a longitudinal axis;

a plurality of discrete ring stents having a plurality of struts andapices between the struts, the apices including proximal apices anddistal apices;

a running suture attaching at least one stent of the plurality of stentsto the graft, the running suture comprising:

at least first and second knots knotted along the length of each strutat intermediate points on the struts away from the proximal and distalapices,

a length of running suture running between the first and a second knotson each strut, and

a first bridging portion extending between a first knot on a first strutadjacent a proximal apex and a first knot on a second strut adjacent theproximal apex, and a second bridging portion extending from a secondknot on a second strut adjacent a distal apex to a second knot on athird strut adjacent the distal apex.

Advantageously, the first bridging portion and the second bridgingportion are disposed transverse to the longitudinal axis of the lumen;and/or

at least a portion of the first and second bridging portions passesthrough the graft; and/or

the running suture is continuous about a circumference of the at leastone stent; and/or

each stent of the plurality of stents comprises a running suture havingfirst and second knots and first and second bridging portions.

According to another aspect of the present invention, there is providedan aortic stent-graft comprising:

a graft having an elongate lumen and a longitudinal axis;

an external zig zag stent having a plurality of struts and apicesbetween the struts, the apices including proximal apices and distalapices, the stent extending around an external circumference of thegraft;

a set of removable proximal sutured knots, the proximal sutured knotssecuring the proximal apices of the stent to the graft;

a set of removable distal sutured knots, the distal sutured knotssecuring the distal apices of the stent to the graft; and

a plurality of intermediate sutured knots separate from the set ofremovable proximal and distal knots, formed along a running suture, therunning suture including a plurality of bridging portions, the bridgingportions disposed transverse to the longitudinal axis of the lumen andbridging between adjacent struts of the stent, the intermediate suturedknots securing struts of the stent to the graft.

Advantageously, the plurality of bridging portions passes into and outof the graft between adjacent struts of the external zig zag stentand/or the running suture is continuous about a circumference of theexternal zig zag stent.

According to an aspect of the invention, there is provided a stent-graftcomprising:

a graft having an elongate lumen and a longitudinal axis;

an external stent having a plurality of struts and apices between thestruts, the apices including proximal apices and distal apices;

a set of proximal sutured knots, the proximal sutured knots securing theproximal apices of the stent to the graft;

a set of distal sutured knots, the distal sutured knots securing thedistal apices of the stent to the graft; and

a plurality of intermediate sutured knots, formed along a continuoussuture, the continuous suture including a plurality of bridgingportions, the bridging portions bridging between neighbouring struts ofthe stent, the intermediate sutured knots securing struts of the stentto the graft.

All aspects of the present invention, may have one or more of thefollowing characteristics.

Advantageously, the bridging portions are disposed transverse to thelongitudinal axis of the lumen.

The plurality of intermediate sutured knots along the continuous suturemay include two or three intermediate sutured knots along each strut ofthe external stent.

The stent is may be zig zag stent. The stent is advantageously selfexpanding.

The zig zag stent preferably extends around an external circumference ofthe graft.

Advantageously, the proximal sutured knots and the distal sutured knotsare locking knots.

The intermediate sutured knots may be over-threaded knots.

Preferably, the stent-graft is an aortic stent-graft.

The bridging portions may pass into and out of the graft such that theyinclude external bridging portions and internal bridging portions.

Preferably, the stent-graft comprises a plurality of external stentsdisposed longitudinally along the graft, each stent having a pluralityof struts and apices between the struts, the apices including proximalapices and distal apices thereby forming peaks and valleys, whereinadjacent stents are positioned such that peaks from one of the pluralityof external stents extend towards or into valleys of another of theplurality of external stents.

Advantageously, the adjacent stents are positioned such that peaks fromone of the plurality of external stents extend into valleys of anotherof the plurality of external stents.

According to another aspect of the invention, there is provided a methodof forming an endoluminal prosthetic device, the method comprising thesteps of:

providing a graft comprising a bio-compatible material and defining amain tubular body;

providing a first external stent comprising a plurality of struts andapices between the struts, the apices including proximal apices anddistal apices;

positioning the first stent around the main tubular body;

joining the proximal apices and the distal apices of the first stent tothe graft using respective sutured proximal knots and sutured distalknots;

joining the struts of the first stent to the graft by intermediatesutured knots in a continuous suture, the continuous suture bridgingbetween neighbouring struts of the stent.

The step of joining the proximal and distal apices of the first stent tothe graft may comprise joining using locking knots.

Advantageously, the step of joining the struts of the first stent to thegraft by knots in a continuous suture comprises passing the continuoussuture into and out of the graft so as to bridge between neighbouringstruts of the stent.

The preferred embodiments will be particularly discussed in relation tostent-grafts for placement into the thoracic abdominal aorta or into theabdominal aorta for the treatment of aneurysms. The teachings herein arenot, however, so restricted and may be applied to stent-grafts or anyother medical device for placement in any lumen of the human or animalbody.

the teachings herein can provide an improved stent graft, other medicaldevice, and an improved method of forming an endoluminal medical device,while improving safety and simplifying assembly.

Other aspects and advantages of the teachings herein will becomeapparent to the skilled person having regard to the specific descriptionthat follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described below, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic isometric view of a stent-graft according to anembodiment of the invention;

FIG. 2 is a detailed view of a portion of the stent-graft shown in FIG.1;

FIGS. 3A and 3B are a similar view to that of FIG. 2, showing a detailedview of a stent-graft according to another embodiment of the invention;

FIG. 4 is a similar view to that of FIG. 2, but shows a detailed view ofa stent-graft according to another embodiment of the invention;

FIG. 5 is a detailed view showing a proximal apex of a stent and aproximal locking knot on a stent-graft according to embodiments of theinvention;

FIG. 6A is an annotated schematic diagram of the suture forming thelocking knot of FIG. 5;

FIGS. 6B and 6C are detailed views of a strut of a stent on astent-graft according to embodiments of the invention;

FIG. 6D is a view showing the tightened suture of the embodiment ofFIGS. 6A to 6C;

FIG. 7A is a detailed view of a strut of a stent on a stent-graftaccording to another embodiment of the invention;

FIG. 7B is a view showing the tightened suture of the embodiment of FIG.7A;

FIG. 8 is a schematic view similar to that of FIG. 5, showing anotherembodiment of locking knot of the tightened suture of the embodiment ofFIG. 7A;

FIGS. 9A to 9C are schematic diagrams showing a method of forming thesuture arrangement of FIGS. 7 and 8;

FIG. 10 shows a stent-graft according to the invention being deployedfrom a delivery device;

FIGS. 11A and 11B an example of branched stent graft in a curved in-useconfiguration and a straight configuration, respectively;

FIG. 12 is a schematic diagram of a prior art suture stent fixationarrangement;

FIGS. 13A to 13C show a stent graft having a sutured stent according toFIG. 12 will curve in use;

FIG. 14 is a schematic diagram of a suture stent fixation arrangement astaught herein;

FIGS. 14A to 14C show a stent graft having a sutured stent according toFIG. 14 will curve in use;

FIG. 15 is a schematic diagram of a stent graft with stents attached tothe graft according to the teachings herein; and

FIG. 16 is a schematic diagram of another embodiment of stent graft withstents attached to the graft according to the teachings herein.

DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERREDEMBODIMENTS

For the purposes of understanding the principles of the teachingsherein, reference will now be made to the embodiments illustrated in thedrawings, and specific language will be used to describe them. It is tobe understood that the Figures are, in some cases, schematic and do notshow the various components in their actual scale. In many instances,the Figures show scaled up components to assist the reader.

Throughout this specification, the term “distal” with respect to aportion of the aorta, a deployment device or an endograft means the endof the aorta, deployment device or endograft further away in thedirection of blood flow from the heart and the term “proximal” means theportion of the aorta deployment device or end of the endograft nearer tothe heart in the direction of blood flow. When applied to other vessels,similar terms such as caudal and cranial should be understood.

Referring to FIG. 1, a stent-graft 10 having a proximal end 11 and adistal end 18 is shown. The stent-graft 10 comprises a graft 20providing an elongate lumen 22 having a longitudinal axis 25 and one ormore external stents 300. Now turning to FIG. 2, it can be seen that theexternal stent 300 has a plurality of struts 351, 352, 353, 354 andapices between the struts, the apices including proximal apices 311,312, 313 and distal apices 381, 382.

In the embodiment of FIG. 1 the stent 300 is a zig zag stent and thatthe zig zag stent is self-expanding. In other embodiments of theinvention, not shown, stents having different geometries may be used.

The zig zag stent 300 extends around an external circumference of thegraft 20. Furthermore, it can be seen that there are a plurality ofexternal stents disposed longitudinally along the graft, in this casethree (3), each stent having a plurality of struts and apices betweenthe struts. Typical examples of such struts and apices are shown moreclearly in FIG. 2 as has been described above. The apices includeproximal apices and distal apices thereby forming peaks and valleys,wherein adjacent stents are positioned such that peaks from one of theplurality of external stents extend towards or into valleys of anotherof the plurality of external stents. In FIG. 1 stent 300 forms a valley310 into which peak 390′ of stent 300′ extends towards. In otherembodiments adjacent struts are attached such that there is some overlapand where the peaks extend into valleys of and adjacent stent. Dependingon requirements including flexibility, kink resistance, and preventingadjacent stents making metal to metal contact, positioning and overlapof adjacent stents can be varied. The term “valley” is intended to meanthe V-shaped space between adjacent struts of a particular stent andapplies irrespective of orientation (whether inverted or conventionalorientation).

The stent-graft 10 shown in FIG. 1 is an aortic stent-graft. However,stent-grafts for other parts of an anatomy may also be providedaccording to the invention. With the aortic stent-graft 10 of FIG. 1, aterminal stent 190 is provided at a proximal end thereof. This terminalstent 190 may be provided with anchoring members in the form of barbs195, such as those shown in FIG. 10. Such barbs 195 help decreasemigration of the stent-graft 10 within the vessel in which it isdeployed. The stent-graft 10 shown in FIG. 1 also includes an internalstent 200 and external stents 300, 300′ and 300″. Many other stent-graftconfigurations are possible and may incorporate the features of theteachings disclosed herein.

While the stents 300 are shown external to the graft tubing in theseembodiments, it is to be understood that they may be disposed internallyof the graft tubing, either all or one or more thereof.

Now referring to FIG. 3A, it can be seen that the stent-graft comprisesa set of proximal sutured knots 411, 412, 413, the proximal suturedknots securing the proximal apices 311, 312, 313 of the stent 300 to thegraft 20. The stent-graft also comprises a set of distal sutured knots481, 482, the distal sutured knots 481,482 securing the distal apices381, 382 of the stent 300 to the graft 20. As explained in furtherdetail below, the proximal and distal sutured knots 411-413 and 481-482may in at least some embodiments be omitted, be removable or be loosesutures, allowing for the stent 300 to slide within the remainingsutures of the assembly.

A plurality of intermediate sutured knots 501 a, 501 b, 502 a, 502 b,503 a, 503 b, 504 a, 504 b, formed along a continuous suture 500, areprovided. The continuous suture 500 includes a plurality of bridgingportions 520, 530, 540 bridging between neighbouring struts of the stent300. The intermediate sutured knots secure the struts of the stent tothe graft 20.

In the embodiment of FIGS. 3A and 3B, the bridging portions 520, 530,540 pass into and out of the graft 20 such that they include externalbridging portions such as 522 and 528 as shown in FIG. 3B, and internalbridging portions, such as 525 also shown in FIG. 3B.

With the embodiments shown in FIGS. 3A and 3B, where the suture has apath through the wall of the graft 20 into and out of the graft 20, soas to bridge between neighbouring struts of the stent, there is lessrisk of the suture 500 catching.

Looking at bridging portion 520 in FIGS. 3A and 3B, it can be seen thatthe bridging portion 520 bridges between knots 501 b and 502 asubstantially circumferentially around a portion of the stent-graftbetween struts 351 and 352. The bridging portion 520 is disposed atalmost exactly 90 degrees to the longitudinal axis 25 of the lumen (asshown in FIG. 1). In other embodiments, the angle at which the bridgingportions are disposed transverse to the longitudinal axis of the lumenmay vary. That is, they may be transverse at an angle other than 90degrees, but still such that they bridge transversely across to theadjacent strut, rather than following along the strut and around itsapex or point.

When FIG. 1 is viewed together with FIG. 2, it can be seen that thebridging portions 520, 530, 540 are in this embodiment disposedtransverse to the longitudinal axis 25 of the lumen 22.

Again referring to FIGS. 1 and 2, it can be seen that the plurality ofintermediate sutured knots along the continuous suture 500 include twointermediate sutured knots along each strut of the external stent 300.In contrast, in another embodiment of the invention shown in FIG. 4,there are three intermediate sutured knots along each strut of theexternal stent. For instance, FIG. 4 shows knots 501 a, 501 b and 501 calong strut 351 of the external stent 300. In yet other embodiments (notshown), four or more intermediate sutured knots along each strut of theexternal stent may be provided depending on factors such as the size ofthe stent-graft. The intermediate sutured knots are preferably spacedevenly along their corresponding strut at 4 to 7 mm apart.

Now referring to FIG. 5, a proximal sutured knot 411 is shown in moredetail. This proximal sutured knot 411 secures an apex 311 to the graft20 with a locking knot formed by two pairs of double knots, sometimesreferred to as reef knots. The proximal sutured knot 411 is a lockingknot, as opposed to a tacking knot. It is a single stitch though thegraft material, but has four knots (two pairs of double knots). Theknots are a left over right knot, then a right over left knot, then aleft over right knot and finally a right over left knot, as can be seenclearly in FIGS. 5 and 6A. Unlike with some prior art stent-grafts, thisknot does not need to be removed.

FIGS. 6B and 6C show a portion of the continuous suture 500 along astrut in a magnified view. In FIG. 6B, a first intermediate knot 501 ahas been tied and a second intermediate knot 501 b is in the first stageof being tied. In FIG. 6C, the second intermediate knot 501 b is stillpartially tied ready for a second knot so that it will match the firstintermediate knot 501 a. FIG. 6D, shows the continuous suture 500 tiedto a graft 21 and in particular the arrangement of the suture at theknots depicted in FIGS. 6B and 6C.

Referring now to FIGS. 7A and 7B, these show another embodiment ofcontinuous suture with a modified knot arrangement compared to that ofthe embodiment of FIGS. 5 to 6D. In the embodiment of FIGS. 7A and 7B,four double knot arrangements 601 a-601 d are formed on the stent struts351 intermediate the apices 412, 481, 482 of the stent. Each double knotof the continuous suture is effectively the same as the other knots 601a-601 d of the continuous suture thread 500. The double knot 601 a isformed by a loop of suture thread passing out of the graft material 21and then back into the graft material at the same side of the stentstrut 351 and from the other side of graft material passes back outagain on the opposite side of the strut 351, to be looped underneath thefirst formed loop, over the stent strut 351, to enter into the otherside of the graft material on the first side of the strut, then loopedout again at the other side of the strut and then passed through theformed second loop on the first side of the strut, before passingtowards the second double loop arrangement. FIG. 7B shows one of thedouble-loop knots depicted in schematic form in FIG. 7A.

Referring to FIG. 8, a proximal sutured knot 611 is shown in moredetail. Similar to the embodiment of FIGS. 5 and 6A, the proximalsutured knot 611 secures an apex 311 to the graft 20 with a locking knotformed by two pairs of double knots, sometimes referred to as reefknots. This provides a staggered stitch with, for each double knot, adouble formed left over right stitch, as can be seen in FIG. 8. Thestaggered stitch is fast to sew and reduces the number of times themanufacturer has to swap tools to complete the sewing process. This canhelp with cross-contamination from handling tools too often and requiresless time to be spent handling the graft during manufacture thereof.

Referring now to FIGS. 9A to 9C, these depict how the double knotarrangement of FIGS. 7A to 8 can be achieved in one manufacturingimplementation. With reference to FIG. 9A, the first knot is loopedtwice around needle holders 650 and tightened. With reference to FIG.9B, the second knot is looped once around the needle holders 650 andtightened, while, with reference to FIG. 9C, the third knot is loopedonce around the needle holders 650 and tightened. Thereafter, the suturetails are cut with a finishing length of, preferably, around 3.0 mm plusor minus 1.0 mm.

Turning now to FIG. 10, a delivery assembly 100 sliding along a guidewire 7 and having an introducer 90 is shown. Such a delivery assembly100 can be used to deliver a stent-graft according to the teachingsherein. The delivery assembly 100 comprises a guide wire catheter 120having a tip 130 mounted to a proximal end 122 thereof. A distaldelivery member 110, which could be referred to as a pusher, is mountedaround the guide wire catheter 120 and is located distal of the tip 130.A stent-graft receiving portion 140 is provided between the tip 130 andthe distal delivery member 110. The delivery assembly 100 is slidablymounted through the introducer 90. A handle 150 is manipulable to slidethe distal delivery member (pusher) 110 through the introducer 90 so asto position the stent-graft 5 in the vascular system of a patient.

FIGS. 11A and 11B show a stent graft having a plurality of stents 300attached to the graft material in a conventional manner, as shown inFIG. 12, that is with a running suture 700 extending along each strut ofthe stent and to each apex. The stent is firmly attached, which resultsin stiffness of the stent graft 700 to bending, as will be apparent fromFIG. 11A and as is known in the art.

Referring now to FIGS. 13A to 13B, these show another embodiment ofstent graft 720 that again has the stents attached to the graft materialby a running suture that extends along the entirety of each strut to theapices thereof. The stents in this example are spaced form one anotherby around 10 millimetres. As can be seen in particular in FIGS. 13B and13C, while the stent spacing allows greater bending of the stent graftcompared to the example of FIGS. 11A and 11B, when curved at arelatively tight angle, as might occur for example in the aortic arch,significant ruffling 730 of the graft material occurs particularly atthe inside of the curve. This ruffling can cause significant turbulencein the flow of fluid (blood) through the stent graft, disrupting normalblood flow and function.

Referring now to FIG. 14, this shows in schematic form anotherembodiment of stent attachment arrangement similar to that of FIG. 2 butin which the stent apices 411-414 and 481-485 do not have any suturesattaching them to the graft material. In other words, the stent 300 isattached to the graft tubing solely by the intermediate running suture500. This may be achieved by use of tack knots that may be removed,degrade or by omitting them entirely. In other embodiments, only loosetack knots may be used that allow sliding of the stent within theconstraints of the intermediate running suture.

While the embodiment of FIG. 14 shows neither the proximal nor thedistal apices 411-414 and 481-485 having any tack knots, in practice itmay be preferred to maintain the proximal tack knots and remove thedistal tack knots.

Referring now to FIGS. 14A to 14C, this shows an embodiment similar tothat of FIG. 14 but in which the proximal bridging portions 530 aredisposed inside the graft tubing, which is an alternative to thearrangement shown in FIG. 14. In practice, the bridging portions 530,540 may weave into and out of the graft material so as in effect to beheld by the material. The intermediate suture arrangement assist in thecontrol of the graft material as the stent graft 10 is curved, as itwould be in a curved vessel, and in particular prevents or substantiallylimits ruffling of graft material at the interior of the curve, as canbe seen by a comparison of FIG. 14C with FIG. 13C.

FIG. 15 shows a stent graft provided with three stents 300, 300′ and300″ having the intermediate suture arrangement of FIG. 14 and free,that is non attached, stent apices.

FIG. 16 shows a slightly modified embodiment, in which the bridgingportions 530′ and 540′ are arranged between adjacent apices of thestents 300, 300′, 300″, that is at the wider ends of the V formed byadjacent struts of the stent.

Preferably, the graft 20 is formed from tube material may be formed froma biocompatible material that is substantially non-toxic in the in vivoenvironment of its intended use and will be substantially not rejectedby the patient's physiological system (i.e., is non-antigenic). Forexample, the graft tube material may be made of an expandedpolytetrafluoroethylene (ePTFE), polytetrafluoroethylene, silicone,polyurethane, polyamide (nylon), polyethylene, polypropylene,polyaramids, polyacrylonitrile, cellulose, or another flexiblebiocompatible material. The graft tube material also may be made ofknown fabric graft materials, e.g., woven polyester such as DACRON® fromInvista (Wichita, Kans.), polyetherurethanes such as THORALON® fromThoratec Corporation (Pleasanton, Calif.), or polyethylene such as anultra-high molecular weight polyethylene (UHMwPE) such as DYNEEMA® fromDSM Dyneema LLC (Stanley, N.C.). In addition, materials that are notinherently biocompatible may be subjected to surface modifications torender the materials biocompatible. Examples of surface modificationsinclude, for example, graft polymerization of biocompatible polymers onthe surface, coating of the surface with a crosslinked biocompatiblepolymer, chemical modification with biocompatible functional groups, orimmobilization of a compatibilizing agent such as heparin or otherbiocompatible substances. Thus, any fibrous material having sufficientstrength to survive in the in vivo environment may be used to form atextile graft, provided the final textile is biocompatible.

The graft tube material may also include a bio-remodelable material suchas reconstituted or naturally-derived collagenous materials. Suitableremodelable materials can be provided by collagenous extracellularmatrix (ECM) materials possessing biotropic properties. For example,suitable collagenous materials may include ECM materials such as thosecomprising submucosa, renal capsule membrane, dermal collagen, duramater, pericardium, fascia lata, serosa, peritoneum or basement membranelayers, including liver basement membrane. Suitable submucosa materialsfor these purposes may include, for instance, intestinal submucosaincluding small intestinal submucosa, stomach submucosa, urinary bladdersubmucosa and uterine submucosa. Collagenous matrices includingsubmucosa (potentially along with other associated tissues) useful inthe present invention can be obtained by harvesting such tissue sourcesand delaminating the submucosa-containing matrix from smooth musclelayers, mucosal layers, and/or other layers occurring in the tissuesource. For additional information as to some of the materials useful inthe present invention, and their isolation and treatment, reference canbe made, for example, to U.S. Pat. Nos. 4,902,508, 5,554,389, 5,993,844,6,206,931, and 6,099,567. A non limiting example of a suitableremodelable material may include SURGISIS® BIODESIGN™ from Cook Medical(Bloomington, Ind.) or the graft prosthesis material described in U.S.Pat. No. 6,206,931 to Cook et al., which is incorporated herein byreference in its entirety. The graft tube material also may be made ofany of the materials described in U.S. Pat. No. 7,407,509 to Greenberget al. or U.S. Patent Application Publication Number 2009/0171451 toKuppurathanam et al., which are incorporated herein by reference intheir entirety.

The stents of the embodiments of the invention, such as stents 200, 300,300′ and 300″, may have any suitable stent pattern known in the art. Thestents may be balloon expandable. Preferably, the stents may beself-expandable. The stents can maintain the patency of the prosthesisand ensure adequate sealing against the surrounding vascular tissue. Onegoal for stent design and placement, whether internal or external, maybe to prevent metal-to-metal contact points, prevent contact between twodifferent types of alloys, and minimize micro-motion. The arrangementshown in FIG. 1, where adjacent stents are positioned such that peaksfrom one of the plurality of external stents extend towards the valleysof another of the plurality of external stents, assist in preventingmetal-to-metal contact points. Stent sizing, spacing, and design may bedetermined so that there is no stent-to-stent contact even in tortuousanatomy. Stents preferably may be placed to maximize prosthesisflexibility while maintaining patency, as well as reduce material wearand stent fatigue. Furthermore, it is preferable that the stents do notinterfere with the branch, that they minimize the potential for galvaniccorrosion and ensure adequate joint stability. Stent amplitude, spacing,and stagger preferably may be optimized for each prosthesis design. Anyof the stents mentioned herein may have barbs and/or other anchoringmembers to help decrease prosthesis migration.

One example of a stent pattern is the Z-stent or Gianturco stent design.Each Z-stent may include a series of substantially straight segments orstruts interconnected by a series of bent segments or bends. The bentsegments may include acute bends or apices. The Z-stents are arranged ina zig zag configuration in which the straight segments are set at anglesrelative to one another and are connected by the bent segments. Thisdesign provides both significant radial force as well as longitudinalsupport. In tortuous anatomy, branches or fenestrations, it may bepreferable to use alternative stents or modifications to the Z-stentdesign to avoid stent-to-stent contact. Alternative stents may include,for example, annular or helical stents. Furthermore, in complexanatomical situations, external stents may have the potential to becomeintertwined with the wires or other devices utilized to ensure branchvessel access, sealing, and fixation. Thus, in some instances, it may bedesirable to affix some of the stents to the internal surface of theprosthesis.

The stents described herein may be made from any suitable material knownin the art. In one example, the stents may be made from standard medicalgrade stainless steel and are soldered using silver standard solder (0lead/0 tin). In other examples, the stents may be made from a metallicmaterial selected from any type of stainless steel, silver, platinum,palladium, gold, titanium, tantalum, iridium, tungsten, cobalt,chromium, cobalt-chromium alloy 1058, cobalt-based 35N alloy,nickel-based alloy 625, a molybdenum alloy, a molybdenum alloy includingabout 0.4% to about 0.8% of lanthanum oxide (Li.sub.20.sub.3), and anickel-titanium alloy, or other suitable materials known in the art. Thestents also may be made from nitinol or other shape-memory metal.Moreover, the stents may be configured in a variety of ways to provide asuitable intraluminal support structure. For example, one or more stentsmay be made from a woven wire structure, a laser-cut cannula, individualinterconnected rings, or another pattern or design.

Stent-grafts according to the teachings herein, such as stent-graft 10,can be made efficiently. They do not require temporary stitches that areused commonly in producing other stent-grafts, particularly those havingexternal stents. This saves considerable time and improves manufacturingefficiency. It is also easier to construct as the sewer does not have toturn the graft upside down continuously as they sew along the strut.Instead, the graft can be held in one position (upright) as the sutureruns along the graft. Making the process easier reduces errors and theneed for re-work.

Aside from being more efficient, avoiding the need for temporary ortacking stitches avoids additional holes being formed in the graftmaterial. Also avoided is the potential for tacking stitches to bemissed and then forming a bio-burden with the patient during or afterendovascular surgery.

Stent-grafts according to the teachings herein, such as stent-graft 10,provide a safer prosthetic in that cuts to the graft material are muchless likely than stent-grafts that utilise temporary stitches (forinstance to initially hold apices in place). Avoiding cuts and holes isimportant because cuts or holes can cause blood leakage into aneurysmalor other areas outside the lumen of the vessel being repaired.

A method of forming an endoluminal prosthetic device, such as is shownin FIGS. 1 and 2, will now be described.

A graft comprising a bio-compatible material, such as the bio-compatiblematerial described above, defining a main tubular body is provided. Afirst external stent is also provided, the first external stentcomprising a plurality of struts and apices between the struts, theapices including proximal apices and distal apices. The first stent 300is positioned around the main tubular body (such as is shown in FIGS. 1and 2). The proximal apices and the distal apices of the first stent arejoined to the graft using respective sutured proximal knots and sutureddistal knots. The struts of the first stent are joined to the graft byintermediate sutured knots in a continuous suture, the continuous sutureridging between neighbouring struts of the stent, as is clearly shown inFIG. 2.

In one embodiment of a method according to the invention, the step ofjoining the proximal and distal apices of the first stent to the graftcomprises using locking knots, such as the locking knot shown in FIG. 5.

In a further method according to the invention, the step of joining thestruts of the first stent to the grafts by knots in a continuous suturecomprises passing the continuous suture into and out of the graft, suchas is shown in FIG. 3A.

It is preferred that the intermediate suture 500 that provides thebridging portions 530, 540 is a continuous suture that extendscircumferentially around the entirety of the stent 300, 300′, 300″. Thisreduces the number of tie knots, optimises compressibility of the stentgraft for deployment and facilitates assembly. However, in someembodiments the running intermediate suture 500 may be provided in aplurality of lengths, that is each would extend only partially aroundthe stent 300, 300′, 300″. It is also possible to have the intermediatesutures 500 as individual bridging portions 530, 540 with the suturetied and terminating at each end of a bridging portion, although this isa less preferred arrangement.

As explained above, one or more or all of the stents 300,300′, 300″,that is the stents provided with intermediate bridging sutures, could bedisposed on the outside of the graft tubing, as in the preferredembodiments described above and shown in the drawings or one or morecould be disposed inside the graft tubing.

Throughout this specification and the claims that follow unless thecontext requires otherwise, the words ‘comprise’ and ‘include’ andvariations such as ‘comprising’ and ‘including’ will be understood toimply the inclusion of a stated integer or group of integers but not theexclusion of any other integer or group of integers.

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgement of any form of suggestion that suchprior art forms part of the common general knowledge.

It will be appreciated by those skilled in the art that the invention isnot restricted in its use to the particular application described or tostent grafts per se, being applicable to other types of implantablemedical devices having a stent or scaffold attached to a support such asa graft material or other membrane. Neither is the present inventionrestricted in its preferred embodiment with regard to the particularelements and/or features described or depicted herein. It will beappreciated that the invention is not limited to the embodiment orembodiments disclosed, but is capable of numerous rearrangements,modifications and substitutions without departing from the scope of theinvention as set forth and defined by the following claims.

The disclosures in U.S. patent application No. 62/716,444 and inAustralian patent application number 2018/214103, from which thisapplication claims priority, and in the abstract accompanying thisapplication are incorporated herein by reference.

1. A stent-graft comprising: a graft defining an elongate lumen having alongitudinal axis; at least one stent having a plurality of struts andan apex between each of the plurality struts, the apices includingproximal apices and distal apices; a running suture attaching the stentto the graft, the running suture comprising: first and second knotsknotted along the length of one or more struts of the plurality ofstruts at intermediate points spaced from the proximal and distalapices, a length of running suture running between the first and secondknots, and a first bridging portion extending between a first knot on afirst strut and a first knot on a second strut next adjacent the firststrut, and a second bridging portion extending from a second knot on thesecond strut to a second knot of a third strut next adjacent the secondstrut.
 2. The stent-graft of claim 1, wherein the first bridging portionis proximal to the second bridging portion.
 3. The stent graft of claim1, wherein the first bridging portion extends between two struts of aproximal apex and the second bridging portion extends between two strutsof a distal apex.
 4. The stent graft of claim 1, wherein the firstbridging portion extends between a first strut of a first proximal apexand a first strut of a second proximal apex.
 5. The stent graft of claim1, wherein a length of the bridging portions passes in and out of thegraft between next adjacent struts.
 6. The stent graft of claim 1,further comprising a series of proximal tack knots securing the one ormore of the proximal apices of the stent to the graft;
 7. The stentgraft of claim 1, further comprising a series of distal tack knotssecuring one or more of the distal apices of the stent to the graft. 8.The stent graft of claim 7, wherein the series of distal tack knots areconfigured such that the stent can slide relative to the graft.
 9. Thestent graft of claim 1, further comprising a third knot in the runningsuture between each of the first and second knots
 10. The stent-graft ofclaim 1, wherein the bridging portions are disposed transverse to thelongitudinal axis of the lumen.
 11. The stent graft of claim 1, whereineach strut of the plurality of struts has a first knot and a second knotand a first bridging portion extending from the first knot and a secondbridging portion extending from the second knot.
 12. The stent-graft ofclaimed claim 1, wherein the running suture is a single continuouslength of suture.
 13. A stent-graft comprising: a graft defining anelongate lumen having a longitudinal axis; a plurality of discrete ringstents having a plurality of struts and apices between the struts, theapices including proximal apices and distal apices; a running sutureattaching at least one stent of the plurality of stents to the graft,the running suture comprising: at least first and second knots knottedalong the length of each strut at intermediate points on the struts awayfrom the proximal and distal apices, a length of running suture runningbetween the first and a second knots on each strut, and a first bridgingportion extending between a first knot on a first strut adjacent aproximal apex and a first knot on a second strut adjacent the proximalapex, and a second bridging portion extending from a second knot on asecond strut adjacent a distal apex to a second knot on a third strutadjacent the distal apex.
 14. The stent-graft of claim 13, wherein thefirst bridging portion and the second bridging portion are disposedtransverse to the longitudinal axis of the lumen.
 15. The stent graft ofclaim 13, wherein at least a portion of the first and second bridgingportions passes through the graft.
 16. The stent graft of claim 13,wherein the running suture is continuous about a circumference of the atleast one stent.
 17. The stent graft of claim 13, wherein each stent ofthe plurality of stents comprises a running suture having first andsecond knots and first and second bridging portions.
 18. An aorticstent-graft comprising: a graft defining an elongate lumen having alongitudinal axis; an external zig zag stent having a plurality ofstruts and apices between the struts, the apices including proximalapices and distal apices, the stent extending around an externalcircumference of the graft; a set of removable proximal sutured knots,the proximal sutured knots securing the proximal apices of the stent tothe graft; a set of removable distal sutured knots, the distal suturedknots securing the distal apices of the stent to the graft; and aplurality of intermediate sutured knots separate from the set ofremovable proximal and distal knots, formed along a running suture, therunning suture including a plurality of bridging portions, the bridgingportions disposed transverse to the longitudinal axis of the lumen andbridging between adjacent struts of the stent, the intermediate suturedknots securing struts of the stent to the graft.
 19. The aortic stentgraft of claim 18, wherein the plurality of bridging portions passesinto and out of the graft between adjacent struts of the external zigzag stent.
 20. The aortic stent graft of claim 18, wherein the runningsuture is continuous about a circumference of the external zig zagstent.